Regional model evaluation of mercury deposition in Florida

To evaluate and identify source-receptor relationships at local scales, and their temporal trends, a modified version of the WRF/Chem model has been developed within he GMOS project, in order to include the emissions, interactions, transport and deposition of atmospheric mercury with high spatial resolution [1]. Anthropogenic and natural (marine and from wildfires) mercury emissions have been included in this model version, and gaseous and aqueous phase oxidation were implemented, while chemical initial and boundary conditions were obtained from ECHMERIT global on-line chemical transport model [2]. Using the WRF/Chem with Hg model simulations of the atmospheric mercury cycle over Gulf of Mexico and Florida for July 2009 have been performed using emissions generated using SMOKE from the U.S. National mission Inventory [3]. Due to the continuing debate over the precise atmospheric Hg oxidation mechanism [3], simulations using a Br/BrO based Hg oxidation mechanism rather than O3/OH were performed. For the period under study the model reproduces Hg wet and dry deposition reasonably well for the more southerly Florida measurement stations, while a large overestimation was found for more central and northern stations. Moreover the model also overestimates the atmospheric Hg measurements, especially using the O3/OH oxidation mechanism. Model results show also a larger fraction of RGM in deposition compared to PBM, while relatively high values of PBM in deposition are found near the main anthropogenic emissions sources.